Computer systems have quickly become the center of numerous operations performed in households throughout the world. Previously, a computer was used only for simple computing operations; however, uses for computers have progressed from this simple model into an electronics hub. A few examples of this progression include using a computer as a media center, a TV, a stereo, and a picture repository. As a result, the amount of internal logic, as well as the need for more input/output (I/O) terminals to communicate with external devices, has drastically increased.
Yet, as interconnects, such as a front-side bus (FSB), continue to increase in speed to ensure adequate bandwidth for integrated circuits, such as microprocessors, signal integrity becomes an ever-more present concern. Degradation of signal quality potentially leads to signaling errors through both voltage level and timing failures. Examples of contributing factors to adverse signal integrity includes distance/amount of a ground return paths, distance between signals, number of signals, impedance mismatches, cross-coupling, and other numerous factors.
In the past, as the number of I/O terminals on a microprocessor and the pins on a package for the microprocessor have increased, the number of ground terminals and pins have been increased to ensure signal quality. For example, past packages have included a signal to ground ration of one ground signal for each two signal carrying pins. However, as stated above, as the number of signals increase, continuing to hold the same signal to ground ratio leads to extremely large packages that are prohibitively expensive. Yet, if signal pins are isolated and do not have adequate ground return paths, the signal quality of high speed signals potentially affects performance.